Portable shavers are equipped with a main switch which turns a motor on/off, and a locking system which stops this function. The locking system is provided to prevent the main switch from being accidentally turned on due to an external shock and the like. As a result, the motor will not rotate and consume battery energy, when the portable shaver is contained and carried in a suitcase or the like.
As a practical means for realizing this locking system, there are known mechanical locking means and electrical means utilizing a slide switch. Mechanical locking means are arranged so that the switch bar of the main switch is mechanically locked to prevent it from moving to the on-position when the main switch is in the off-position, and the main switch is not mechanically locked when the main switch is in the on-position. On the other hand, as shown in FIG. 1, with the locking system using electrical means, a locked state is realized by turning a lock slide switch 28, which is connected in series with a main switch 27, to the off-position, so that the power to the load will be cut off.
In recent years, push type switches have come into use widely as the main switch. The push type switches are a type of switch turned on/off by depressing a switch button, and there are types in which the depressed state is held (alternate type) and types in which the depressed state returns to the previous state as soon as the finger is removed (momentary type). Especially, soft touch momentary type switches are used frequently nowadays.
In battery operated portable shavers utilizing a momentary type switch as the main switch (hereinafter referred to as momentary switch type shavers), a pulse is generated each time the main switch is depressed, and the switched state is held by means of a state holding circuit until the next pulse is sent.
As shown in FIG. 1, in conventional shavers in which an alternate type main switch 27 and a lock switch 28 are connected in series, the rotation of a motor 23 is stopped when the lock switch 28 is turned on with the main switch 27 in the on state. Thus, the motor can be stopped not only by the main switch but also by the lock switch. This results in a problem in that it is difficult to determine which switch is the main switch.
Such a problem does not exist when a mechanical locking system is used. However, locking means utilizing a mechanical means cannot be used in momentary switch type shavers. This is because a switch on/off signal cannot be sent to the state holding circuit when the main switch operation is disabled by the mechanical means. On the other hand, if a microprocessor is used, it is possible to realize a momentary switch type shaver in which the function of the main switch and lock switch are clearly separated. However, microprocessors are rather expensive and require expensive development costs for deriving its software.
Momentary type switches have recently come into use not only in shavers as mentioned above, but as the main switch of headphone stereo sets. However, headphone stereo sets are conventionally not equipped with a lock switch. Therefore, when a headphone stereo set having this type of main switch is carried in a pocket and the like, there is a problem that the main switch can be depressed, and the headphone stereo set operates, and consequently the battery energy is consumed completely.